The present invention generally relates to data storage devices. More specifically, the present invention relates to removable cartridge storage devices.
Computer backup has traditionally been performed using tape drive technologies. Tape drive technologies have been popular in the use of backup systems for a variety of reasons. One reason is that tape media has generally had the lowest cost per bit of storage. Additionally, tape devices use removable tape cartridges, which may be taken to an off-site location to provide for disaster recovery. A third reason tape devices are popular is because of the long-term archive characteristics of tape media.
As the storage capacity in stand-alone and networked computers has increased, so have the demands on backup systems. One of the current trends is the use of mechanical automation systems, such as tape cartridge autoloaders and robotic tape libraries, to expand the capacity of the backup system. The cartridge autoloaders and tape libraries hold multiple removable tape cartridges. One or more tape drives is embedded inside a storage area containing one or more magazines of tape cartridges. These systems also include a mechanical system to automate the cartridge changing operation. The mechanical system is used to load and unload the cartridges between the magazines and the tape drives.
A prior art tape cartridge autoloader that may be used to automate cartridge changing operations is illustrated in FIG. 1. The tape autoloader 100 includes at least one tape drive 120. Multiple storage slots 111-117 are used to house tape cartridges 101-107. The storage slots 111-117 may be part of a removable magazine to facilitate the loading and unloading of cartridges.
A motorized mechanism 130 is used to move the tape cartridges 101-107 to and from the tape drive 120. The motorized mechanism may also optionally be used to move cartridges to and from an access opening (not shown) to the tape autoloader 100, which may be used to enter and remove tape cartridges 101-107 into the tape autoloader 100. The motorized mechanism 100 may include a cartridge picker arm 134 and a picker motor 132 to operate the cartridge picker arm 134. A drive motor 136 is used to drive the motorized mechanism 130.
The tape autoloader 100 typically has at least two interfaces 152, 154 to host computer 150. By way of example, interfaces 152, 154 may be Small Computer System Interfaces (SCSI) or Fiber Channel (FC)interfaces. An interface 154 is provided for each tape drive 120 included in the tape autoloader. This interface 154 may be referred to as the “data path” interface and is used to send data and tape drive commands to a system controller component of tape drive 120. The tape autoloader 100 may include multiple tape drives and the data path interfaces to each tape drive may be coupled to different host computers. A second interface 152 (also called the “control path”) is used to send control commands to the autoloader mechanism controller 140, such as load, unload, and audit commands. The autoloader mechanism controller 140 includes electronics and software used to actuate the motorized mechanism 130 f 6 r movement of tape cartridges 101-107 and auditing of the tape autoloader 100. The control path interface 152 may be coupled to a second host computer. Some prior art tape autoloaders combine the functions of the “data path” and “control path” interfaces into a single physical interface.
The autoloader mechanism controller 140 is also communicatively coupled to tape drive 120 for communications between these components. Although multiple tape drives in the tape autoloader 100 may be operated in parallel, the mechanical system 130 used to load and unload cartridges can only move a single cartridge at a time. A separate “data path” interface to host computer 150 is required for each tape drive 120, as each tape drive has its own system controller.
As can be appreciated from the above description, the tape cartridge autoloader 100 can only hold a predetermined number of data cartridges 111-117. Other types of prior art autoloader devices (e.g., optical autoloader devices) also have the same limitation. Although these systems come in may different sizes and cartridge capacities, buyers may face a difficult dilemma when determining the capacity of the device that will best meet organizational requirements. Buyers may choose to either purchase a smaller capacity autoloader device to meet current needs and replace the device when capacity requirements increase or may choose to purchase a larger capacity device to meet future expected capacity requirements. The first alternative is disruptive when the organization/application upgrades to a larger capacity device and more costly since two devices are purchased. The second alternative has a high initial cost which may not be affordable or may be perceived to be unnecessary as larger capacity requirements may not be anticipated.